* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
li {
  list-style: none;
}
.product {
  width: 800px;
  margin: 0 auto;
  height: 100px;
  background-color: green;
}
#nav {
  width: 100%;
  height: 100px;
  background-color: #ccc;
  overflow: hidden;
}
ul {
  width: 1280px;
  height: 100%;
}
li {
  position: relative;
  float: left;
  width: 240px;
  height: 60px;
  margin: 20px 0;
  text-align: center;
  line-height: 60px;
}
li + li {
  margin-left: 20px;
}
li:nth-child(1) {
  background-color: yellowgreen;
}
li:nth-child(2) {
  background-color: greenyellow;
}
li:nth-child(3) {
  background-color: gold;
}
li:nth-child(4) {
  background-color: plum;
}
li:nth-child(5) {
  background-color: skyblue;
}
.line {
  position: absolute;
  top: 0;
  left: 50%;
  width: 1px;
  height: 100%;
  background-color: blue;
}
.center {
  width: 1px;
  height: 100px;
  margin: 0 auto;
  background-color: red;
}
